Dry, flowable, water-dispersible granular (hereinafter sometimes referred to as "WG") formulations of agricultural chemicals have achieved recent commercial popularity since they tend to be safer to apply and more environmentally friendly due to the ease by which such formulations may be handled. For examples, WG formulations of agricultural chemicals can eliminate the need for aromatic solvents thus reducing or eliminating volatile organic compounds. WG formulations also greatly reduce worker exposure to the chemical and usually reduce the overall toxicity of the formulations because of greatly reduced dust and aromatic solvents.
Furthermore, agricultural chemicals in the form of WG formulations will typically leave lesser residue on the interior surfaces of container packaging as compared to the same agricultural chemicals in the form of an emulsifiable concentrate or wettable powder. To eliminate all packaging residue, it has been proposed to provide water-dispersible granular formulations of agricultural chemicals in water-soluble bags so that the entire package (i.e., the water-soluble bag and the water-dispersible granules of agricultural chemicals contained therein) can simply be added to an appropriate amount of water prior to application. In this regard, please see International Application Nos. WO 92/17381 published on Oct. 15, 1992; WO 92/17385 published on Oct. 15, 1992; and WO 92/17383 published on Oct. 15, 1992, as well as European patent Application Nos. 0518629 A1 published on Dec. 16, 1992 and 0518689 A1 published on Dec. 16, 1992, the entire content of each such publication being incorporated expressly hereinto by reference. Agricultural chemicals in the form of water-dispersible gels which may or may not be contained within such water-soluble bags have been proposed as evidenced by International Application Nos. WO 92/01378; WO 92/01374; WO 92/01377; WO 92/10376 and WO 92/01375, the entire content of each such publication being incorporated expressly hereinto by reference.
Providing water-dispersible agricultural chemicals to the end users in a container system which is water-soluble is clearly advantageous in terms of reduced container residue--i.e., since no container physically remains after the agricultural chemical has been dispersed in water. However, providing WG agricultural chemicals pre-packaged in water-soluble containers has some disadvantages. For example, the water-soluble bag will sometimes break during transport and/or handling thereby completely nullifying any advantage in terms of chemical residue and/or reduced exposure which the bag was intended to provide. Furthermore, there is reduced flexibility in terms of chemical application rate since the entire water-soluble bag containing a pre-measured amount of the granular agricultural formulations is intended to be placed directly in water prior to application. That is, varying chemical application rates are very difficult to achieve by the user since the granular agricultural chemicals are packaged in pre-measured amounts which may not always meet the needs of the particular crop application. Furthermore, trace amounts of agricultural chemical can occur outside the water-soluble bag due to dust associated with commercial filling operations.
Therefore, what has been needed in this art is a suitable way to supply WG agricultural chemicals to the end user in a manner which significantly reduces (or eliminates entirely) chemical residue on interior surfaces of non-water-soluble containers while, at the same time, does not adversely affect the water-dispersibility property of the WG agricultural chemicals and provides the end-user with application rate flexibility. It is towards fulfilling such a need that the present invention is directed.
Broadly, the present invention is embodied in water dispersible agricultural chemical formulations wherein the individual granules are coated with a water-soluble film. The water-soluble film coating on the granules thus significantly reduces or eliminates any chemical residue on interior surfaces of containers used to package the formulations for transport/handling, while providing the end-user with a variety of crop application rates--i.e., since the entire package does not need to be used. A critical part of the present invention is that this coating is accomplished without significantly adversely affecting the dispersibility characteristics of the granules.
In preferred forms, the present invention is embodied in water dispersible agricultural chemical formulations wherein the water-soluble coating consists essentially of polyvinyl alcohol, sodium silicate, alkyl and hydroxyalkyl cellulose (e.g., methyl, propyl and ethyl cellulose and hydroxy methyl, hydroxypropyl and hydroxyethyl cellulose), polyethylene oxide, such as polyethylene glycol, starch and modified starch, carboxymethylcellulose, polyvinylethers such as polymethyl vinylether or poly(2-methoxyethoxyethylene), poly(2,4-dimethyl-6-triazinylethylene, poly(3-morpholinyl ethylene), poly(N-1,2,4-triazolylethylene), poly(vinylsulfonic acid), polyanhydrides, low molecular weight melamineformaldehyde resins, low molecular weight urea-formaldehyde resins, poly(2-hydroxyethyl methacrylate), polyacrylic acid and its homologs. Most preferably, however, the water-soluble coating consists essentially of polyvinyl alcohol.
Further aspects and advantages of this invention will become more clear after careful consideration is given to the detailed description of the preferred exemplary embodiments thereof which follows.